Formation marking system

ABSTRACT

The particular embodiment described herein as illustrative of one form of the invention utilizes, in a drilling system, capsules which are moved at high velocities out the eye of the drill bit to be impacted with the formation being drilled. Marking materials in the capsules are thereby embedded within the formation. In one embodiment, explosive charges fracture rock formations while the drilling operation is taking place. A radioactive substance is included in the charge for marking the formation to identify and correlate the formation material at drilling depth.

United States Patent [72] Inventors John D. Bennett;

Stanley B. McCaleb, Richardson, Tex. [21] Appl. No. 787,065 [22] Filed Dec. 26, 1968 [45] Patented Mar. 2, 1971 73] Assignee Sun Oil Company Philadelphia, Pa.

[54] FORMATION MARKING SYSTEM 2,868,506 1/1959 Nestle 175/42 3,022,729 2/1962 Robinson 175/2 3,054,938 9/1962 Meddick 166/297X 3,130,797 4/1964 Johnson 175/4.5 3,155,176 11/1964 Bennett 175/42 Primary ExaminerStephen J. Novosad Assistant Examiner Richard E. Favreau Attorneys-George L. Church, Donald R. Johnson, Wilmer E.

McCorquodale, Jr. and John E. Holder ABSTRACT: The particular embodiment described herein as illustrative of one form of the invention utilizes, in a drilling system, capsules which are moved at high velocities out the eye of the drill bit to be impacted with the formation being drilled. Marking materials, in the capsules are thereby embedded within the formation. In one embodiment, explosive charges fracture rock formations while the drilling operation is taking place. A radioactive substance is included in the charge for marking the formation to identify and correlate the formation material at drilling depth.

PATENTEU um 2 .u'IA ArA FIG. 2

INVENTORS JOHN D. BENNETT STANLEY B. M CALEB m AT TORNE Y FORMATION MARKING SYSTEM BACKGROUND OF THE INVENTION This invention relates to a formation marking system, and more particularly, to a system of marking formation materials during the drilling operation.

In borehole drilling, various geological formations and materials are penetrated during the drilling of a well. As

recovered in cores and cuttings, these materials are studied by the geologist and the petroleum engineer to determine the position of the well on the structure in relation to other wells which have been drilled, and to establish the position of the materials in the geological column. The information concerning the penetration of formations provides valuable information to the geologist and petroleum engineer as to formation breaks and geological structures.

Oil and gas wells are now being located, spaced,.drilled, and produced on a more scientific basis than-was the case in the past. Modern practices require an accurate and detailed knowledge of subsurfaceconditions in order that the well may be completed properly. Depth, thickness, and the nature of formations include perhaps the most useful information shown by the well log, while other more detailed data suchas fluid content, porosity, permeability and dip are also available to the producer as well as to the drilling operator. These data can most easily be obtained from uncontaminated cores. Cores also provide the best answers to many other pertinent questions. However, the taking of sidewall cores, for example, requires the lowering of a gum into the well, which fires coretaking barrels laterally into the formation and retrieval of the tool to recover the cores. Because the drilling of the well must be stopped during this operation, and the facilities of a service company normally are required to run the service, such procedures are very expensive. It is often the case that the quantitative information obtainable by cores is not absolutely necessary, and that the core is used to provide accurate data as to the exact location of formation breaks. If this latter is the case, another technique for determining such exact breaks would be equally as useful with the coring only being done in .thosesituations where it is desirable to obtain quantitative data such as porosity and permeability. Electric logs are also a method used to determine exact correlation between depth and formation breaks. Again, this procedure requires the stopping of a drilling operation and, for the most part, the removal of the drill string during the logging operation.

The reason for determining the exact stratigraphic levels encountered in a wellbore column are many fold. The most obvious reason is to determine the stratigraphic picture of the wellbore in order to determine the location of oil-bearing sands from information already known from existing wells. There are many other reasons for gathering such information, including the following: During formation testing it is desirable to set a packer into the formation being tested so as not to expose the test to formations above that zone. In this situation, it is desirable to know the exact level of such breaks in the formations. In addition, when it is expedient to take cores of the formation to obtain qualitative data therefrom, it is helpful to know the exact depths at which to start the core taking procedure, so that more valuable information may be derived therefrom. Thisrequires that knowledge of the formation break be derived beforehand. Also, it is often necessary to complete a well at a certain depth, being careful not to 'go beyond such depth. For example, if you have an oil column on top of a water column, and you do not wish to penetrate the water column, and thereby produce from such column, it is necessary to stop within the oil columnbefore such penetration takes place. In these circumstances, if the approximate thickness of the oil column is known, and if the formation break at the top of the column is known with preciseness, it is possible to reach a maximum depth within the oil column and preclude penetration of the water column.

Another situation requiring accurate information as to formations penetrated occurs when leases are obtained requiring wells to be drilled to and only to a certain formation. Under such circumstances, the exact position of the drilling operation at any time can be an important factor. Also, information as to formation breaks can be valuable in determining when lectric logs or other qualitative formation testing techniques are desirable.

In the past, one of the most common methods used for determining formation breaks has been to observe the time that it takes for the circulating mud column to move from the bottom of the wellbore to the surface. Oftentimes, articles were circulated withinthe mud system which were identifiable at the surface to determine the circulation time. In addition, other formation marking techniques such as that disclosed in US. Pat. No. 3,115,176 involve the use of dyes or dye marking materials which were ejected into the drilling mud for circulation to the'surface so that a determination could be made as to the time that it takes to move the muds and thus the formation materials from the wellbore to the surface. This latter technique has the disadvantage of the possibility of a miscorrelation between a time it would take a dye to reach the surface and the time it would take a drill cutting to reach the surface. A drill cutting, being more dense, tends to settle within the drilling mud column, whereas the dye tends to follow the liquid and less dense constituents of the mud, so that exact depth correlation is not likely. A determination of the circulation time by means of observing articles circulated within the mud system is also unreliable, in that mud circulation. is affected by density of the mud,,pump pressure, loss of circula' tion, water encroachment, etc., with such factors adding enough variables to prevent exact correlations.

a technique for determining the exact location of a formation break would not only provide the obvious advantage of being able to locate such a break, but would also permit a correction factor to be applied to the time of circulating mud in a drilling system so that subsequently more accurate determinations could be made from the use of this latter technique which is described above.

It is therefore an object of the present invention to provide a new and improved system for determining the exact location of the origin of formation cuttings within a borehole.

SUMMARY OF THE INVENTION With this and other objects in view, the present invention contemplates a technique for moving marking devices within the circulating mud through a drill stem and passing such devices into the borehole beneath the drilling bit for impact therewith. Marking materials, contained within the device are implanted in the formation being penetrated by the drill bit. Such formation materials are circulated by the mud to the surface. The implanted marking materials in the formation permit an exact determination of he depth at which the formation materials were cut, since the exact depth at which the device was impacted intothe formation may be determined.

A complete understanding of this invention may be had by reference to the following detailed description, when read in conjunction with the accompanying drawings illustrating an embodiment thereof.

BRIEFDESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. I shows merely as an example, a drilling rig which is substantially conventional and which may be used for the practice of the invention. Many other drilling rigs may be used which may also be substantially conventional, involving only minor changes for practice of the invention. There is indicated at 5 a hook which is connected to the usual traveling blocks supported by cables and controlled by the draw-works of a derrick (not shown). A bail 7 hung on the hook supports the conventional swivel 6. The swivel 6 is joined at 8 with the usual kelly 10, passing through the rotary table 12, by which it is driven in supporting the sectional drill stem 14 in conventional fashion. The drill stem extends downwardly into a wellbore'and terminates in the usual drill collar 18 (FIG. 2). Various conventional parts of the assembly are not indicated, but it will be understood that they are provided as in usual drilling practices.

The drill collar 18 carries a bit 20 which is illustrated as of the multiple cone type, of which one of the cones is indicated at 22. Jet openings, between the cones, are provided at 26. Liners 24 are positioned within the openings for resisting abrasion of the mud.

The mud flows to swivel 6 through a flexible hose 36, which is supplied with mud from the usual high pressure mud pump which is not shown. The main flow takes place through a conduit 40. Bypass flow to carry the explosive members into the hose 36, swivel 6, and the hollow drill stem takes place through a feeding means 38 for the explosive members. Feeding means 38 is provided with inlet and outlet passages 66 and 68, the latter being of a size to pass the explosive members The passages 66 and 68 are joined at their inlet and-outlet ends respectively with the mud conduit 40. The feeding means is provided with a feeding mechanism which may be operated automatically to feed explosive members into the mud stream selectively in order that they may be passed through the mud line into the wellbore. The details of such a feeding apparatus are set forth in U.S. Pat. No. 3,130,797, issued to F. L. Johnson.

A typical explosive member which may be used is designated generally as 42, and is shown in section in FIG. 3 of the drawings. In the particular form illustrated, the explosive member comprises a main housing 44, a lower protective cap 46, and an upper'protective cap 48. The upper protective cap is primarily for the purpose of giving the member sufficient length for longitudinal guidance and prevention of inversion of position in the connections through which it moves. These parts of the explosive member 42 are preferably formed of either plastic, glass, or ceramic, being designed to withstand the pressure encountered within the drill stern and the various shocks to which it may be subjected in passing through the system and into the opening in the bit. A frangible metal may also be used for these parts so long as it conforms to the desirable requirements that these parts should be broken up by the explosion, should not weld to or otherwise become jammed in the opening within the bit, and should be broken up in the operation of the bit. The lower cap 46 should be of such thickness that while it will withstand the mud pressures, it will be crushed if the member is ejected through the opening in the bit. The velocity of the jet flow is conventionally very high to the end that the explosive member will be ejected against the bottom of the hole at a very high velocity so as to effect pressure on the cap and as will appear, firing.

The interior of the housing 44 contains a charge 50 of high explosive, desirably in the form of a shaped charge with a conical hollow in its lower end lined by a cone 52, of thin material which may be a metal, plastic, ceramic, etc. A distance of space is provided below the conically shaped lower end of the charge and the bottom of the housing to provide a standoff between the charge and the bottom of the hole. A tube 60 of similar material passes through the center of the charge 50 for the guidance of a metallic firing pin 58, the upper end of which underlies the detonator 56 molded into the charge 50. Above the upper end of the charge is a cap disc 54, which may be of ceramic or plastic.

The particular details of the explosive member is subject to a great variety of choice. The art of shaping charges such as at 52, for securing a very great variety of effects, is highly developed and well known, and reference may be made to many patents and articles thereof for discussion of variations. The shaped charges give rise to what is known as the Munroe Effect. Generally the ends of these charges which are to produce the effectof the explosion are conical or otherwise hollowed to provide more or less directed jets, depending upon the results desired. For military uses where piercing of armor is the primary desire, the cavities in the charges are generally truly conical and the explosive at the time of firing is required to be of particular standoff distance from the surface which is to be penetrated. In such cases, the cone liner corresponding to 52 is generally of metal and the theory of operation is that this metal is formed and projected at extremely.

high velocity to penetrate the target in the form of a clean hole. On the other hand, where a shattering effect is desired, as in blasting, the cavities are sometimes more or less dome shaped as outlined by a plurality of conical surfaces with the effect of spreading the explosive wave for action over a larger area. Since, in the present case, such shattering action is desired, formation of the cavity for optimum shattering action is desirable.

In the instant apparatus, the purpose is to implant detectable substances within the formation being drilled, and therefore, it is necessary to provide such detectable substances either within the shaped charge or in the standoff cavity between the cone and the end of the housing. In the embodiment shown herein, it is suggested that the cone material itself be constructed to a material which may be an amalgam of a metal such as copper and a radioactive material, such as a radioactive isotope. Alternatively, the copper may be mixed with a suspension of a radioactive powder. In any event, the radioactive material should not be appreciably soluble in water, salt, or other materials normally encountered either in the drilling matter or the formation fluids encountered in a well bore. A few of the potential radioactive elements for use in such an apparatus are: Co 56, Sr 90, Zn 65, Th 228, and U 233. The materials may be alpha, beta, or gamma emitters depending upon the necessary life of the material. Also, one or more materials may be used to cover various ranges of desired performance. The construction of the explosive device to include the radioactive materials and the selection of the material will depend upon many factors including cost, type of mud, kind of rock, its density and stability, the type of formation fluid and drilling mud, the relative safety of the material, and many other factors which would be considered in the handling and use of such devices. Additionally, other types of marking materials might be used in the construction of the explosive device described above, such materials having the capability of being implantable or otherwise making or imparting a characteristic to the formation material being drilled which is detectable in the material at the surface.

The upper end cap of the apparatus provides an upright member to prevent the apparatus from tumbling or turning sideways within the flow line or drill stem. This insures proper orientation of the explosive apparatus as it nears the lower end of the drill stem wherein the increased acceleration of the mud flow towards and into the eyes of the'bit will guide the explosive members through the eye of the bit for impact with the earth formation therebelow. This engagement or impact of the apparatus with the formation will occur at a very high velocity, since the mud circulation is continuing, and the velocities involved are essentially those of a jet drilling operation. The nose cap is constructed so as to be deformed or even shattered upon engaging the formation at such velocity, and when this occurs, the firing pin will be retarded to fire the detonator and ignite the high explosive.

The firing will occur within an extremely small fraction of time, and therefore will take place while the lower conical end of the explosive is substantially spaced from the bottom of the hole. The usual standoff space is thus provided which has been recognized as desirable in the use of shaped charges. It will be noted that this standoff space is primarily an air space, permitting the shaped charge to form, however, this space could be partially filled by material such as for marking the formation. The exploding charge will cause penetration and disruption of the earth formation adjacent to the bottom of the hole in view of the fact that the effected region is bound by solid and liquid (the mud).. The shattering. effect is widespread rather than involving merelythe production of a clean hole irrespective of the shape of the explosive. As pointed out above, the shape may be chosen in accordance with the known practices to augment the shattering effect. All the material of the explosion will either be vaporized or shattered in the form of small particles so that nothing remains which would impede the further progress of the rotating drill bit. e

vAs the explosive is detonated and the shapedcharge takes form and moves into the formation, particles of the cone member, which disintegrates in the process, will become implanted within the earth formation, which may also be shattered by the explosion or subsequentlygroundup by the drill bit, such portions of the earth formation with the implanted particles will be moved upwardly to the surface in the mud stream. When such matter reachesthe surface in the mud stream, detectors (not shown) of any well-known type for detecting radioactive materials may be used to detect the presence of such materials at the surface. Uponthe engagement of the radioactive materials with the formation, both primary and secondary radiation may take placePrimary radiation is radiation resulting from the host material embedded within the formation. Secondary radiation, on the other hand, a is a result of the earth materials being exposed to the host material and bombarded by radioactiveemissions therefrom.

For, example, ifv the formation were an unconsolidated sand which would not readily be embedded with particles from the explosive charge, the host material particles would still be dispersed within the formation materials and carried therewith or, induced radiation of the unconsolidated sand particles would provide a means forassociating thedetecting material with the earth formation material present in the wellbore at the time the shaped charge explosion occurs. On the other hand, harder and more consolidated rock materials will readily capture particles containing the host materials so thatupon removal to the surface in the mud stream, the detection of the host materials within the formation materials would provide a direct correlation between depth and earth formation.

.with a detectable markerenclosedtherein so that upon impact of the housing with the formation, such marker material would be sufficiently dispersed within the formation, even in the absence of any explosion, to cause its movement in the mud system to the surface similar to that manner described relative to the explosive chapges. The drilling operation would further facilitate the embed mg of such marker materials in the formation cuttings. d

The above described procedure provides techniques for correlating depth and materials at the surface of which the following are examples: A direct correlation between depth and materials is possible, since it was known at what drilling depth the explosion takes place, and it can be observed what materials are moved to the surface with implanted detectable matter therein. This provides a direct and accuzratedetermination of a specific formation at a specific depth. In addition, various acousticaldetecting devices may be employed to determine at the surface the exact .moment detonation. Because of this and other time check procedures, it is possible to determine how long it is taking cuttings at the current rate of drilling, mud circulation, etc., to reach the surface so that more accurate information can be obtained as to depth correlation using this prior-art technique to supplement the use of explosive charges. 9

While particular embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changesand modifications as fall within the true spirit and scope ofthis invention.

I claim: I

1. A method of marking and identifying earth formation materials while a drilling operation is taking place, comprising the steps of:,placing an explosive device within a drill string at the surface of the well being drilled, such explosive device having a marker material therein; circulating a drilling fluid through the drill string to move the explosive device through the drill string and out the eye of a drill bit attached thereto;

impacting the explosive device onto the formation being drilled to initiate and explosion; implanting exploding particles including the marking materials into the earth formation for marking the formation, such marking material having identifiable features; recording the depth at which such exploln the operation of the system described above, during a.

drilling operation, if it is desired to obtain information relative,

to formation characteristics at a particular depth, an explosive capsule is released from the dispensing mechanism in the mud flow line and moves through the flow line, the drill stem, an d drill bit into impact with-the bottom of the wellbore, whereupen the explosive charge is detonated and the resulting jet is generated to implant the radioactive or otherwise detectable materials within the formation. Of course, the implanted materials may cause induced radiationof the formation materials to provide a detectable marker. lnany event, after the detonation and implantation of thedetectable materials,

such materials which are either loosened from the formation:

sion takes place; continuing the circulation of drilling fluid to move chips of-earth formation implanted with marking material to the surface; detecting at the surface, such marking material; identifying the earth formation carrying the marking material; and correlating the type of formation with the depth at which the marking material was implanted therein.

2. A method of identifying earth formations during a drilling operation, comprising the steps ofz placing a device within a drill string at the surface of a well being drilled, applying fluid pressure to the interior of the drill string to move the device through and out the lower end of the drill string; impacting the device onto the formation being drilled; implanting particles into the earth formation for marking the formation, such particles having'identifiable features; continuing the application of fluid pressure to the drill string to move the material im- I planted with such particles to the surface; and detecting and identifying at the surface the formation materials implanted with such particles.

3. The method of claim 2 wherein said device utilizes an explosive charge, and further. includes the step of detonating said explosive charge at the bottom of the well. 

1. A method of marking and identifying earth formation materials while a drilling operation is taking place, comprising the steps of: placing an explosive device within a drill string at the surface of the well being drilled, such explosive device having a marker material therein; circulating a drilling fluid through the drill string to move the explosive device through the drill String and out the eye of a drill bit attached thereto; impacting the explosive device onto the formation being drilled to initiate and explosion; implanting exploding particles including the marking materials into the earth formation for marking the formation, such marking material having identifiable features; recording the depth at which such explosion takes place; continuing the circulation of drilling fluid to move chips of earth formation implanted with marking material to the surface; detecting at the surface, such marking material; identifying the earth formation carrying the marking material; and correlating the type of formation with the depth at which the marking material was implanted therein.
 2. A method of identifying earth formations during a drilling operation, comprising the steps of: placing a device within a drill string at the surface of a well being drilled, applying fluid pressure to the interior of the drill string to move the device through and out the lower end of the drill string; impacting the device onto the formation being drilled; implanting particles into the earth formation for marking the formation, such particles having identifiable features; continuing the application of fluid pressure to the drill string to move the material implanted with such particles to the surface; and detecting and identifying at the surface the formation materials implanted with such particles.
 3. The method of claim 2 wherein said device utilizes an explosive charge, and further includes the step of detonating said explosive charge at the bottom of the well.
 4. The method of claim 2 wherein the implanted particles are a radioactive material. 